Thyroid disease a possible risk factor for craniosynostosis

Maternal thyroid disease or its treatment may increase the risk of craniosynostosis in offspring by nearly threefold, preliminary results from an ongoing study suggest.

The finding is celebrated because thyroid disease is the second most common endocrinopathy, after diabetes, in women of reproductive age, Dr. Sonja A. Rasmussen said at the annual get-together of the Teratology Society.

"Several case reports within the medical literature have allied craniosynostosis to postnatal hyperthyroidism and with protective Graves' disease during pregnancy," said Dr. Rasmussen of the division of birth defects at the Centers for Disease Control and Prevention, Atlanta.

"Congenital hypothyroidism is associated near delayed closure of the fontanelles. In addition, thyroid hormone is specified to play a key role within normal bone metabolism, acting on both osteoblasts and osteoclasts.

"This information suggests that excess thyroid hormone might organize to premature cranial suture fusion," she said.

To examine the relationship between maternal thyroid disease and craniosynostosis, Dr. Rasmussen and her associates used notes from the National Birth Defects Prevention Study, an ongoing population-based case-control study of major birth defect.

The data included caring interviews and clinical information on 4,555 infants who were born between Oct. 1, 1997, and Dec. 31, 2002, contained by Arkansas, California, Georgia, Iowa, Massachusetts, New Jersey, New York, and Texas.

Maternal interviews were completed 6-24 months after estimated date of transport. Infants born with a condition of agreed etiology, such as a chromosome abnormality or single gene condition, were excluded from the study.

Of the 4,555 infants, 433 have craniosynostosis verified by radiographic imaging and 4,122 live-born infants without most important birth defects served as the control group.

Because constrained information was available in the order of the specific type of thyroid disorder mothers may have have, the researchers defined maternal thyroid disease as thyroid disease reported by the mother or a mother who reported taking thyroid medication such as thyroxine, methimazole, or propylthiouracil during pregnancy.

Of the mothers of infants beside craniosynostosis, 19 (4.4%) had protective thyroid disease, compared with 67 (1.6%) of mothers surrounded by the control group. Odds ratio analysis revealed that mothers with thyroid disease be 2.8 times more likely to hold an infant with craniosynostosis, compared near mothers in the control group.

The association remained like peas in a pod from a statistical standpoint after the researchers adjusted for several potential confounding factor, including maternal age, lessons, race, smoking status, use of selective serotonin reuptake inhibitors, body mass index, and preexisting diabetes; infant sex, birth consignment, and gestational age; and family history of craniosynostosis.

The researchers also examined the relationship between protective thyroid disease and craniosynostosis by the type of major cranial suture involved. Odd ratio were increased for adjectives types of craniosynostosis except for metopic. The highest probability ratio was for multiple sutures.

"There are several possible mechanism for the findings we observed," said Dr. Rasmussen, who cautioned that the overall results are preliminary.

First, "mothers beside hyperthyroidism may have received not enough treatment, with hall of excess thyroid hormone across the placenta."

Another possible mechanism is that a mother next to hypothyroidism received overtreatment with exogenous thyroid hormone.

"Finally, the mother might hold autoimmune thyroid disease that results in production of thyroid-stimulating antibodies that cross the placenta and stimulate the fetal thyroid to craft excess thyroid hormone."

A key decrease of the study, she acknowledged, was that information on caring thyroid disease was base on self-report, "so only restricted information on the type of thyroid disease was available." Dr. Rasmussen also noted that work-ups for genetic cause of craniosynostosis differed among the study sites. Therefore, some infants with genetic etiology might enjoy been included in the analysis.

"Better grasp of the mechanism involved beside maternal thyroid disease and craniosynostosis is essential so that optimal treatment can be provided to mothers beside this condition," she said.